1. Field
The disclosed embodiments relate to an aircraft wing arrangement of the type comprising a wing and also at least one pylon for suspending an engine below this same wing.
More specifically, the disclosed embodiments relate to a wing arrangement for an aircraft whose wings have high-lift devices which are interrupted at the interface between the wing and a pylon, resulting in a reduction of the lift capabilities of the wing during flight at a high angle of attack.
2. Brief Description of Related Developments
In modern aircraft, more specifically civilian transport aircraft, it is known practice to suspend the engines below the wing structure using suspension pylons.
Such pylons are working structures which transmit the forces generated by the engines to the structure of the aircraft and additionally serve to route fuel systems, electrical systems, hydraulic systems and air systems between the engine and the aircraft.
The position of the engines in relation to the wing is the result of a compromise. For aerodynamic reasons, the engines are preferably placed so as to maximize the distance between the engine and the wing.
For reasons of engine ground clearance when the aircraft is on the ground, it is not possible, however, for the engines to be placed much below the wing structure. Given the various installation constraints, it is common for the engines to be positioned below the wing and essentially forward of the leading edge of the wing in the continuation of the local chord of the wing, at which local chord the pylon is fastened.
Moreover, the wings of the aircraft are generally provided with a high-lift device, for example comprising slats, which is situated in particular at the leading edge of said wings.
This high-lift device, arranged at the leading edge over most of the span, is able to move between:                a retracted position in which the nominal profile of the wing in cruise mode is ensured, and        at least one deployed position in which said high-lift device is deployed forward of the aircraft and downward.        
The deployed position is most particularly used in reduced-speed flight phases, when the angle of attack of the aircraft is high in order to reduce the flight speed, for the purpose of increasing the lift coefficients of the wings.
On account of the pylons which hold the engines in place, it is necessary to interrupt the high-lift device at the pylon in order to avoid mechanical interference with said pylon, in particular in the case of swept wings.
This interruption in the high-lift device introduces a discontinuity in the leading edge when said device is in the deployed position, this being the source of aerodynamic flow disturbances. The interruption in the high-lift device in the region of the pylon is a cause of premature airflow separations on the suction side of the wing, these separations degrading the aerodynamic performance of the aircraft and, in particular, the maximum value of the lift coefficient of the wing.
In order to reduce the negative effects associated with interrupting the high-lift device on the leading edge of the wing structure, it is known from patent FR 2555960 to use a bent pylon which, in the region of the leading edge, is locally perpendicular to said leading edge. The high-lift device, which for reasons of mechanical installation likewise moves perpendicularly to the leading edge when it is deployed, can then be adjusted to reduce the spacing between said deployed device and the pylon so as to limit the discontinuity in the leading edge.
This solution has the disadvantage of requiring a pylon of complex geometry whose shape is not compatible with a maximum reduction of drag in cruise mode.
It is also known from U.S. Pat. No. 3,744,745 to position vanes on the nacelles of the engines, these vanes, when at an angle of attack, generating vortices which propagate over the suction side of the wing in the interrupted region of the high-lift device and delay the occurrence of aerodynamic separations.
This solution has the disadvantage of introducing a drag penalty when the aircraft is in cruise mode. Furthermore, given their dimensions, it may prove a difficult operation to install the vanes on account of the movable elements of the nacelle and the need for precise aerodynamic positioning.
Moreover, the vanes may introduce constraints in the conditions of interchangeability of an engine, with its nacelle, when the engine can be fitted on various models of aircraft including some without vanes or with different vanes.